public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }


public void Mirror(TreeNode root){
	if(root==null){
		return null;
		}	
	TreeNode tmp=root.left;
	root.left=root.right;
	root.right=tmp;
	Mirror(root.left);
	Mirror(root.right);
	}
}